From: Steven Rostedt rostedt@goodmis.org
[ Upstream commit bcba8d4dbe6880ce9883409df486de35d3946704 ]
Instead of saving off the text and data pointers and using them to compare with the current boot's text and data pointers, just save off the KASLR offset. Then that can be used to figure out how to read the previous boots buffer.
The last_boot_info will now show this offset, but only if it is for a previous boot:
~# cat instances/boot_mapped/last_boot_info 39000000 [kernel]
~# echo function > instances/boot_mapped/current_tracer ~# cat instances/boot_mapped/last_boot_info # Current
If the KASLR offset saved is for the current boot, the last_boot_info will show the value of "current".
Cc: Mark Rutland mark.rutland@arm.com Cc: Mathieu Desnoyers mathieu.desnoyers@efficios.com Cc: Andrew Morton akpm@linux-foundation.org Link: https://lore.kernel.org/20250305164608.274956504@goodmis.org Reviewed-by: Masami Hiramatsu (Google) mhiramat@kernel.org Signed-off-by: Steven Rostedt (Google) rostedt@goodmis.org Signed-off-by: Sasha Levin sashal@kernel.org --- include/linux/ring_buffer.h | 3 +-- kernel/trace/ring_buffer.c | 31 ++++++++++++------------------- kernel/trace/trace.c | 30 +++++++++++++++++++++--------- kernel/trace/trace.h | 9 +++++---- 4 files changed, 39 insertions(+), 34 deletions(-)
diff --git a/include/linux/ring_buffer.h b/include/linux/ring_buffer.h index 17fbb78552952..8de035f4f0d9a 100644 --- a/include/linux/ring_buffer.h +++ b/include/linux/ring_buffer.h @@ -94,8 +94,7 @@ struct trace_buffer *__ring_buffer_alloc_range(unsigned long size, unsigned flag unsigned long range_size, struct lock_class_key *key);
-bool ring_buffer_last_boot_delta(struct trace_buffer *buffer, long *text, - long *data); +bool ring_buffer_last_boot_delta(struct trace_buffer *buffer, unsigned long *kaslr_addr);
/* * Because the ring buffer is generic, if other users of the ring buffer get diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index 9b8ce8f4ff9b3..e18d961f4bbd1 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -31,6 +31,7 @@
#include <asm/local64.h> #include <asm/local.h> +#include <asm/setup.h>
#include "trace.h"
@@ -49,8 +50,7 @@ static void update_pages_handler(struct work_struct *work); struct ring_buffer_meta { int magic; int struct_size; - unsigned long text_addr; - unsigned long data_addr; + unsigned long kaslr_addr; unsigned long first_buffer; unsigned long head_buffer; unsigned long commit_buffer; @@ -550,8 +550,7 @@ struct trace_buffer { unsigned long range_addr_start; unsigned long range_addr_end;
- long last_text_delta; - long last_data_delta; + unsigned long kaslr_addr;
unsigned int subbuf_size; unsigned int subbuf_order; @@ -1891,16 +1890,13 @@ static void rb_meta_validate_events(struct ring_buffer_per_cpu *cpu_buffer) } }
-/* Used to calculate data delta */ -static char rb_data_ptr[] = ""; - -#define THIS_TEXT_PTR ((unsigned long)rb_meta_init_text_addr) -#define THIS_DATA_PTR ((unsigned long)rb_data_ptr) - static void rb_meta_init_text_addr(struct ring_buffer_meta *meta) { - meta->text_addr = THIS_TEXT_PTR; - meta->data_addr = THIS_DATA_PTR; +#ifdef CONFIG_RANDOMIZE_BASE + meta->kaslr_addr = kaslr_offset(); +#else + meta->kaslr_addr = 0; +#endif }
static void rb_range_meta_init(struct trace_buffer *buffer, int nr_pages) @@ -1928,8 +1924,7 @@ static void rb_range_meta_init(struct trace_buffer *buffer, int nr_pages) meta->first_buffer += delta; meta->head_buffer += delta; meta->commit_buffer += delta; - buffer->last_text_delta = THIS_TEXT_PTR - meta->text_addr; - buffer->last_data_delta = THIS_DATA_PTR - meta->data_addr; + buffer->kaslr_addr = meta->kaslr_addr; continue; }
@@ -2482,17 +2477,15 @@ struct trace_buffer *__ring_buffer_alloc_range(unsigned long size, unsigned flag * * Returns: The true if the delta is non zero */ -bool ring_buffer_last_boot_delta(struct trace_buffer *buffer, long *text, - long *data) +bool ring_buffer_last_boot_delta(struct trace_buffer *buffer, unsigned long *kaslr_addr) { if (!buffer) return false;
- if (!buffer->last_text_delta) + if (!buffer->kaslr_addr) return false;
- *text = buffer->last_text_delta; - *data = buffer->last_data_delta; + *kaslr_addr = buffer->kaslr_addr;
return true; } diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 50aa6d5908329..ccadd8c657e1a 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -50,7 +50,7 @@ #include <linux/irq_work.h> #include <linux/workqueue.h>
-#include <asm/setup.h> /* COMMAND_LINE_SIZE */ +#include <asm/setup.h> /* COMMAND_LINE_SIZE and kaslr_offset() */
#include "trace.h" #include "trace_output.h" @@ -4193,7 +4193,7 @@ static enum print_line_t print_trace_fmt(struct trace_iterator *iter) * safe to use if the array has delta offsets * Force printing via the fields. */ - if ((tr->text_delta || tr->data_delta) && + if ((tr->text_delta) && event->type > __TRACE_LAST_TYPE) return print_event_fields(iter, event);
@@ -5990,7 +5990,7 @@ ssize_t tracing_resize_ring_buffer(struct trace_array *tr,
static void update_last_data(struct trace_array *tr) { - if (!tr->text_delta && !tr->data_delta) + if (!(tr->flags & TRACE_ARRAY_FL_LAST_BOOT)) return;
/* @@ -6003,7 +6003,8 @@ static void update_last_data(struct trace_array *tr)
/* Using current data now */ tr->text_delta = 0; - tr->data_delta = 0; + + tr->flags &= ~TRACE_ARRAY_FL_LAST_BOOT; }
/** @@ -6821,8 +6822,17 @@ tracing_last_boot_read(struct file *filp, char __user *ubuf, size_t cnt, loff_t
seq_buf_init(&seq, buf, 64);
- seq_buf_printf(&seq, "text delta:\t%ld\n", tr->text_delta); - seq_buf_printf(&seq, "data delta:\t%ld\n", tr->data_delta); + /* + * Do not leak KASLR address. This only shows the KASLR address of + * the last boot. When the ring buffer is started, the LAST_BOOT + * flag gets cleared, and this should only report "current". + * Otherwise it shows the KASLR address from the previous boot which + * should not be the same as the current boot. + */ + if (tr->flags & TRACE_ARRAY_FL_LAST_BOOT) + seq_buf_printf(&seq, "%lx\t[kernel]\n", tr->kaslr_addr); + else + seq_buf_puts(&seq, "# Current\n");
return simple_read_from_buffer(ubuf, cnt, ppos, buf, seq_buf_used(&seq)); } @@ -9210,8 +9220,10 @@ allocate_trace_buffer(struct trace_array *tr, struct array_buffer *buf, int size tr->range_addr_start, tr->range_addr_size);
- ring_buffer_last_boot_delta(buf->buffer, - &tr->text_delta, &tr->data_delta); +#ifdef CONFIG_RANDOMIZE_BASE + if (ring_buffer_last_boot_delta(buf->buffer, &tr->kaslr_addr)) + tr->text_delta = kaslr_offset() - tr->kaslr_addr; +#endif /* * This is basically the same as a mapped buffer, * with the same restrictions. @@ -10469,7 +10481,7 @@ __init static void enable_instances(void) * to it. */ if (start) { - tr->flags |= TRACE_ARRAY_FL_BOOT; + tr->flags |= TRACE_ARRAY_FL_BOOT | TRACE_ARRAY_FL_LAST_BOOT; tr->ref++; }
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h index 9c21ba45b7af6..abe8169c3e879 100644 --- a/kernel/trace/trace.h +++ b/kernel/trace/trace.h @@ -348,8 +348,8 @@ struct trace_array { unsigned int mapped; unsigned long range_addr_start; unsigned long range_addr_size; + unsigned long kaslr_addr; long text_delta; - long data_delta;
struct trace_pid_list __rcu *filtered_pids; struct trace_pid_list __rcu *filtered_no_pids; @@ -433,9 +433,10 @@ struct trace_array { };
enum { - TRACE_ARRAY_FL_GLOBAL = BIT(0), - TRACE_ARRAY_FL_BOOT = BIT(1), - TRACE_ARRAY_FL_MOD_INIT = BIT(2), + TRACE_ARRAY_FL_GLOBAL = BIT(0), + TRACE_ARRAY_FL_BOOT = BIT(1), + TRACE_ARRAY_FL_LAST_BOOT = BIT(2), + TRACE_ARRAY_FL_MOD_INIT = BIT(3), };
#ifdef CONFIG_MODULES